Download Microbial Flora of the Human Body

Microbial Flora of Human Body
(Normal Flora)
NORMAL FLORA:
These are mixture of micro-organisms
regularly found at any anatomical site
on or within the body of a healthy
person.
Factors influencing normal flora:
• The makeup of the normal flora depends upon various
factors, including:
– Genetics
– Age
– Sex
– Stress
– Nutrition
– Diet
– Antiobiotic & other drugs
Normal Microbial Flora:
• 1. Resident Flora:
– Microbes that are always present on or within body
• 2. Transient Flora:
– Microbes that live in or on your body for a period of
time (hours, days, weeks, months) then move on or
die off
Anatomical sites involved:
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Skin
Eyes (i.e Conjunctiva)
Nose (i.e Respiratory tract)
Mouth (i.e Human Oral Cavity)
Ears
Genitourinary tract
Alimentary canal
EXAMPLES OF TISSUE TROPISM OF SOME
BACTERIA ASSOCIATED WITH HUMANS
BACTERIUM
TISSUE
Corynebacterium diphtheriae
Throat
Neisseria gonorrhoeae
Urogenital epithelium
Streptococcus mutans
Tooth surfaces
Streptococcus salivarius
Tongue surfaces
Vibrio cholerae
Small intestine epithelium
Escherichia coli
Small intestine epithelium
Staphylococcus aureus
Nasal membranes
Staphylococcus epidermidis
Skin
Normal flora of Skin:
• Important bacteria:
1.Staphylococcus epidermidis
2. Micrococcus sp.
3. Corynebacterium sp.
4. Mycobacterium smegmatis
Normal Flora of the Conjunctiva:
1. Staphylococcus epidermidis
2. Corynebacterium spp.
3. Propoinibacterium acnes)
4. Staphylococcus aureus
5. Viridans streptococci
6. Neisseria spp.
7. Haemophilus influenzae
Normal Flora of the Respiratory Tract:
A). The nares (nostrils) :
1. Staphylococcus epidermidis
2. Corynebacteria spp.
3. Staphylococcus aureus
4. Neisseria spp.
5. Haemophilus spp.
6. Streptococcus pneumoniae
Normal Flora of the Respiratory Tract:
B) The upper respiratory tract (nasopharynx):
1. Non-hemolytic streptococci
2. Alpha-hemolytic streptococci
3. Neisseria spp.
4. Streptococcus pneumoniae
5. Streptococcus pyogenes
6. Haemophilus influenzae
7. Neisseria meningitidis
Normal Flora of the Respiratory Tract:
C) The lower respiratory tract:(trachea, bronchi, and
pulmonary tissues):
• Usually sterile.
• The individual may become susceptible to infection by
pathogens descending from the nasopharynx:
e.g. H. influenzae,
S. pneumoniae
Sputum Sample
Normal Flora of the Human Oral Cavity:
Oral bacteria include:
1. Viridans streptococci
2. Lactobacilli
3. Staphylococci (S. aureus and S. epidermidis)
4. Corynebacterium sp.
5. Bacteroides sp.
6. Streptococcus sanguis (dental plaque)
7. Streptococcus mutans (dental plaque)
8. Actinomyces sp.
The Normal Flora of The Ears (i.e. external ear)
The external ears contains a variety of
microorganisms. These include:
1. Staphylococcus epidermidis
2. Staphylococcus aureus
3. Corynebacterium sp
Normal flora of the Urogenital Tract:
a) The anterior urethra:
1. Staphylococcus epidermidis
2. Enterococcus faecalis
3. Alpha-hemolytic streptococci.
4. Some enteric bacteria (e.g. E. coli, Proteus sp.)
5. Corynebacteria sp.
6. Acinetobacter sp.
7. Mycoplasma sp.
8. Candida sp.
9. Mycobacterium smegmatis
Normal flora of the Urogenital Tract:
b) The vagina:
1. Corynebacterium sp.
2. Staphylococci
3. Non-pyogenic streptococci
4. Escherichia coli
5. Lactobacillus acidophilus*
6. Flavobacterium sp.
7. Clostridium sp.
8. Viridans streptococci
9. Other Enterobacteria
Vaginal Flora:
Urethritis:
Normal flora - Gastrointestinal tract
Location (adult)
Bacteria/gram
contents
Duodenum
103-106
Jejunum and ileum
105-108
Caecum and
transverse colon
108-1010
Sigmoid colon and
rectum
1011
Normal Flora of the Gastrointestinal Tract
(GIT):
• In breast-fed infants :
1. Bifidobacteria account for more than 90% of the total
intestinal bacteria.
2. Enterobacteriaceae
3. Enterococci
4. Bacteroides
5. Staphylococci
6. Lactobacilli
7. Clostridia
Normal Flora of the Gastrointestinal Tract
(GIT):
• In bottle-fed infants:
• Bifidobacteria are not predominant. When breast-fed
infants are switched to a diet of cow's milk or solid food,
bifidobacteria are progressively joined by:
1. Enterics
2. Bacteroides
3. Enterococci
4. Lactobacilli
5. Clostridia
Normal Flora of the Gastrointestinal Tract
(GIT):
In the upper GIT of adult humans mainly acidtolerant lactobacilli present:
e.g. Helicobacter pylori
Normal Flora of the Gastrointestinal Tract
(GIT):
• The proximal small intestine:
1. Lactobacilli
2. Enterococcus faecalis
3. Coliforms
4. Bacteroides
The flora of the large intestine (colon):
1. Enterococci
2. Clostridia
3. Lactobacilli
4. Bacteroides
5. Bifidobacterium (Bifidobacterium bifidum)
6. Escherichia coli
7. Methanogenic bacteria
8. Viridans streptococci
9. Staphylococcus sp.
10. Proteus sp.
11. Candida albicans (Yeast)
12. Mycoplama sp.
THE ROLE/ BENEFITS OF THE NORMAL FLORA:
1. The normal flora synthesize and excrete vitamins in
excess of their own needs, which can be absorbed as
nutrients by the host.
For example, enteric bacteria secrete Vitamin K and
Vitamin B12, and lactic acid bacteria produce certain Bvitamins.
THE ROLE/ BENEFITS OF THE NORMAL FLORA:
2. The normal flora prevent colonization by pathogens by
competing for attachment sites or for essential nutrients.
This important beneficial effect, which has been
demonstrated in the oral cavity, the intestine, the skin,
and the vaginal epithelium.
THE ROLE/ BENEFITS OF THE NORMAL FLORA:
3. The normal flora may antagonize other bacteria
through the production of substances which
inhibit or kill non-indigenous species.
The intestinal bacteria produce a variety of
substances like nonspecific fatty acids, peroxides
and highly specific bacteriocins, which inhibit or
kill other bacteria.
THE ROLE/ BENEFITS OF THE NORMAL
FLORA:
4. The normal flora stimulates the development of
certain tissues, i.e., the caecum (in animals) and
certain lymphatic tissues (Peyer's patches) in the
GI tract.
The caecum of germ-free animals is enlarged, thinwalled, and fluid-filled, compared to that organ
in conventional animals.
THE ROLE/ BENEFITS OF THE NORMAL
FLORA:
5. The normal flora stimulates the production of “crossreactive antibodies’’.
Since the normal flora behave as antigens in an animal,
they induce an antibody-mediated immune (AMI)
response.
Low levels of antibodies produced against components of
the normal flora are known to cross react with certain
related pathogens, and thereby prevent infection or
invasion.
Sterile tissues:
In a healthy human, the internal tissues
such as:
• blood
• brain
• muscle
• Cerebrospinal fluid (CSF)
are normally free of microorganisms.
Role of Microbiologist:
Accurate diagnosis:
by Rapid/ quick, meaningful reporting
Role of Physician:
Proper treatment with antimicrobial regimen/
standard guidelines
by avoiding overuse*/ misuse of antimicrobials
* by treating pathogen, NOT the normal flora!!
NATURAL MICROBIAL HABITATS
Soil
Water
Air
Animals and Animal Products
HOST
DISEASE
TRIAD
PATHOGEN
Microbial Interactions
OTHER MICROBES
ENVIRONMENT
Symbiotic Relationship:
• 1. Mutualistic/ mutualism:
– Both organisms benefit – “mutually benefical”
• 2. Commensalistic/ commensalism:
– One organism benefits, the other is neither helped nor
harmed
• 3. Opportunistic:
– Under normal conditions, microbe does not cause
disease, but if conditions become conducive , it can
cause disease. (Immuno-compromised or immuno-
Mutualistic:
• Escherichia coli :
– Synthesizes Vitamin K & B complex Vitamins
– In return, we provide a warm, moist nutrient
rich environment for Escherichia coli
Commensalistic:
• We have no Commensalistic relationships with Bacteria
• If Bacteria are in or on our body, they are either helping
us (Microbial Antagonism) or harming us.
Opportunistic:
• Escherichia coli - normally in our digestive tract where it
causes no problems, but if it gets into the urinary tract it
can become pathogenic.
• Staphylococcus aureus – commonly found in the upper
respiratory tract, but if it gets into a wound or a burn it
can become pathogenic
Probiotics/ Prebiotics:
• Probiotic:
– Oral administration of living organisms to promote
health
– Species specific: adherence and growth (tropism)
• Prebiotic:
– Non-digestible food that stimulates growth or activity
of GI microbiota, especially bifidobacteria and
lactobacillus bacteria
– Typically a carbohydrate: soluble fiber
Gnotobiology:
• Gnotobiotic animals: “germfree” (axenic)
– Fetus is sterile
• Cesarean sections to obtain fetus
• Fetus growing in sterile isolator
• Not anatomically or physiologically normal
– Poorly developed lymphoid system, thin intestinal wall,
enlarged cecum, low antibody titers
– Die of intestinal atonia ( motility problem)
– Require vitamin K and B complexes
– No dental caries or plaque
• More susceptible to pathogens
KEY QUESTIONS:
1. Define normal microbial flora. Mention the role/
benefits of normal flora in human body.
2. Normal flora of mouth and upper respiratory
tract.
3. Normal flora of skin.
4. Normal flora of gastro-intestinal tract.
5. Normal flora of genitourinary tract.
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